Full text loading...
Schematic layout of the HEMT structure and measurement method. The polarization-induced 2DEG is characterized by a sheet carrier concentration of and mobility of . Ohmic Ti/Al source-drain contacts (S-D) are electro-chemically isolated from the electrolyte and are driven by a floating circuit, offset by a potential relative to the electrolyte gate using a potentiostat with the Ag/AgCl reference electrode (RE) regulated to zero by a Pt counter electrode (CE).
Source-drain current of an AlGaN/GaN HEMT as a function of dose-rate (X-rays, 150 kV). The insets show the measurement of the absolute source-drain current as a function of time under pulsed x-ray irradiation with various dose-rates of both alternating (left inset) and intermittent (right inset) intensity. The numbers in the insets give the dose rates in mGy/s. The complete experiment, including two irradiation series, was performed twice.
(a), (b) Time integral of the transistor signal shows a linear correlation with the total dose in air. A typical response signal for a dose rate of is given in inset (c). The inset (d) shows an in-going drift of the signal at the beginning of the pulse, but linear behavior is observed down to . The measurements in the low dose range were performed with 18 kV x-rays and the high dose measurements with 150 kV x-rays. Transistors were irradiated for 10 min at different dose rates.
(a) Characteristic curves of a GaN-device in solution before, during, and after irradiation with a dose-rate of 2.9 mGy/s at and . To achieve equilibrium, was first cycled between 0 and −4 V five times. The plotted data were then obtained by averaging of five consecutive cycles per data series. (b) Titration during a continuous irradiation with a dose-rate of 1.4 mGy/s. The slope of the linear response yields a transistor sensitivity of . The inset (c) illustrates a section of the measured gate voltage at different titrated -values. Continuous irradiation was performed with 150 kV x-rays.
Article metrics loading...